1. Field of the Invention
The present invention relates to an electrowetting lens, and more particularly, to an electrowetting lens which can change an optical axis thereof using a multiple electrode structure.
2. Description of the Related Art
Various liquid lenses using electrowetting effect are well known. FIGS. 1A and 1B are schematic cross-sectional views illustrating a conventional electrowetting lens 10. Referring to FIG. 1A, the conventional electrowetting lens 10 includes a substrate 11, a dielectric barrier wall 12 vertically formed on the substrate 11, and polar and non-polar solutions 13 and 14, respectively, filled in the dielectric barrier wall 12. For example, the polar solution 13 may be water, and the non-polar solution 14 may be oil. In this case, since the water is heavier than the oil, the polar solution 13 is placed under the non-polar solution 14, as shown in FIG. 1A. First electrodes 15 are horizontally disposed on the substrate 11. In more detail, the first electrodes 15 are inserted through lower portions of the dielectric barrier wall 12 and make contact with the polar solution 13. Second electrodes 16 are vertically disposed in legs of the dielectric barrier wall 12.
Although not shown in FIG. 1A, inner surfaces 12a of the dielectric barrier wall 12 are coated with a hydrophobic material. Therefore, the polar solution 13 tends to reduce contact area with the inner surfaces 12a of the dielectric barrier wall 12, and the non-polar solution 14 tends to increase contact area with the inner surfaces 12a. As a result, as shown in FIG. 1A, the polar solution 13 has a convex top surface. In this case, the electrowetting lens 10 functions as a convex lens when the polar solution 13 has a refractive index larger than a refractive index of the non-polar solution 14.
When a voltage is applied to the first and second electrodes 15 and 16 using a power supply 17, the dielectric barrier wall 12 is electrically charged as shown in FIG. 1B. Then, the inner surfaces 12a of the dielectric barrier wall 12 changes from hydrophobic to hydrophilic. Therefore, unlike in FIG. 1A, the polar solution 13 tends to increase contact area with the inner surfaces 12a, and the non-polar solution 14 tends to decrease contact area with the inner surfaces 12a. As a result, as shown in FIG. 1B, the top surface of the polar solution 13 is concaved.
FIGS. 2A and 2B are schematic cross-sectional views illustrating another conventional electrowetting lens 20 providing zooming and focusing functions. Referring to FIG. 2A, the conventional electrowetting lens 20 includes a polar solution 21 filled in a tub, a non-polar solution 22 located in the middle of the polar solution 21, first electrodes 23 contacting the polar solution 21, second electrodes 24, third electrodes 25, fourth electrodes 26, fifth electrodes 26′, sixth electrodes 25′, and seventh electrodes 24′. The second through seventh electrodes 24, 25, 26, 26′, 25′, and 24′ are disposed around the tub. Initially, symmetric voltages are applied to the second to seventh electrodes 24, 25, 26, 26′, 25′, and 24′ so as to keep the non-polar solution 22 in a convex state. That is, the same voltages are respectively applied to the second and seventh electrodes 24 and 24′, the third and sixth electrodes 25 and 25′, and the fourth and fifth electrodes 26 and 26′.
Referring to FIG. 2B, a right portion of the polar solution 21 is moved to the left using a pump 28 and a conduit 27. Then, the convex non-polar solution 22 is moved to the right as indicated by the arrow indicating a moving direction of the non-polar solution 22 in FIG. 2A. Here, voltages to electrodes located in the moving direction of the non-polar solution 22 are increased, and voltages to electrodes located in the opposite direction to the moving direction of the non-polar solution 22 are decreased. In this manner, the non-polar solution 22 can be moved back and forth for zooming and focusing. However, the optical axis of the conventional electrowetting lenses cannot be adjusted for controlling an optical path.